Hypocomplementemic urticarial vasculitis syndrome.

Hypocomplementemic urticarial vasculitis syndrome (HUVS) is an uncommon immune complex-mediated entity characterized by urticaria with persistent acquired hypocomplementemia. First described in 1973, HUVS is associated with several systemic findings including leukocytoclastic vasculitis, severe angioedema, laryngeal edema, pulmonary involvement, arthritis, arthralgia, glomerulonephritis, and uveitis. These manifestations should be present for at least 6 months. Laboratory findings include low complement levels of classical pathway, namely C1q, C2, C3, and C4. The disease marker is the serum presence of anti-C1q antibodies. Treatment, based on disease severity, involves corticosteroids and other immunosuppressive agents that have demonstrated some success. Patients may have significant morbidity and mortality, most commonly caused by chronic obstructive pulmonary disease and acute laryngeal edema.